EFFECTS OF BACTERIAL INOCULATION AND NONIONIC SURFACTANTS ON DEGRADATION OF POLYCYCLIC AROMATIC-HYDROCARBONS IN SOIL

The aim of the study was to examine the effects of introduced bacteria and nonionic surfactants on the degradation of polycyclic aromatic hy drocarbons (PAHs) in soil. Mineralization experiments were conducted w ith freshly added [C-14]phenanthrene or [C-14]pyrene, whereas other ex periments focused on the degradation of selected PAHs present in a coa l tar-contaminated soil. Inoculation of soil samples with phenanthrene -utilizing bacteria stimulated the mineralization of [C-14]phenanthren e. This effect, however, was most notable in soil with a low indigenou s potential for PAH degradation, and a large inoculum was apparently r equired to establish phenanthrene mineralization in the soil. Addition of alcohol ethoxylate and glycoside surfactants to soil samples enhan ced the mineralization of [C-14]phenanthrene and [C-14]pyrene. The non ionic surfactants also enhanced the degradation of contaminant PAHs th at were present in the soil coal tar. As an example, pyrene, benzo[b,j ,k]fluoranthene, and benzo[a]pyrene were resistant to degradation in t he absence of surfactants, whereas significant degradation of these PA Hs was observed when surfactants were added. The surfactant-related en hancement of the degradation of PAH contaminants was less convincing w hen a rapidly degradable glycoside surfactant was used. This suggests that surfactants that are mineralized at moderate rates may be more ap plicable for increasing the availability of PAHs in soil.